Across:
1 Give a job cleaning (DUST-) in hospital (-ER) (DUSTER) to a handy one from the board (white/blackboard = DUSTER),
4 She clued (she clued = SCHEDULE) puzzle (= anagram indicator) to plan (SCHEDULE),
9 Brags about (VAUNTS) five (V-) members of the extended family (-AUNTS) (VAUNTS),
10 Turns up (= reversal indicator), objective (goal/end) is cut short (d) (‘end’ without ‘d’ = en = -NE-) in period of rule (reign = -NGI-ER) by Oriental (east = E-) (ENGINEER) mastermind (stage-manage/control = ENGINEER),
12 Listen (LEND AN EAR) behind Guildenstern (behind ‘Guildenstern’ = -N-) and Hamlet (Hamlet/Dane = -D AN E-) in Lear? (LE- - AR) (LEND AN EAR),
13 Sweetheart has no share (‘sweetheart’ has no ‘share’ = wetet = TWEET) in online correspondence (TWEET),
14 Small overseas hotel (PENSION) with plots (PLANS) (PENSION PLANS) guaranteeing an income when the work is finished (PENSION PLANS),
18 Forced to retire (PENSIONED OFF) as 14 across is starting (starting ‘pension plans’ = PENSION-) and energy (energy = -E-) coming from party (-D O-) is very loud (forte fortissimo = -FF) (PENSIONED OFF),
21 Dodge successfully (AVERT) a (A-) very unfinished (‘very’ unfinished = -VER-) square (-T square) (AVERT),
22 Strange (= anagram indicator) sale (sale = ALE -S) includes accommodation (-HOUSE-) (ALEHOUSES) with draughty buildings perhaps? (ALEHOUSES),
24 One (-I-) should have cheated leaders (‘should have cheated’ leaders = shc- = -SH C-) in fraud (fraud = F--AKE) (FISH CAKE) cooked up by the seafood chef (FISH CAKE),
25 No art in satirical (no “art” in “satirical” = siical = SILICA) piece coming from The Stones perhaps (SILICA),
26 Leo’s tuba (Leo’s tuba = ABSOLUTE) played (= anagram indicator) in total without qualification (ABSOLUTE),
27 Slag off gear levers (‘slag’ off ‘gear levers’ = erever = REVERE) or worship? (REVERE).
Down:
1 Old leader (de Valera = DEV-) from Orient (east = -E-) clips (-LOPS) (DEVELOPS) blossoms (DEVELOPS),
2 Jaw-dropping (STUNNING) local deception (ST-ING) involves nun (nun = -UNN-) on the run (= anagram indicator) (STUNNING),
3 Taximeter doesn’t include time (‘taximeter’ doesn’t include ‘time’ = axter = EXTRA) bonus (EXTRA),
5 Cringe (cringe/cower = C- -OWER) over broadcast (-ON-) by troll (troll) briefly (l) (‘troll’ without ‘l’ = -TROL) starting trouble (starting ‘trouble’ = T-) (CONTROL TOWER) that’s capable of restricting access to JFK? (CONTROL TOWER),
6 In reality, lifestyle (EXISTENCE) of sixteen (sixteen = EXISTEN-) mobilised (= anagram indicator) by church (Church of England = -CE) (EXISTENCE),
7 Going through a rough patch (UNEVEN) as not going steady? (UNEVEN),
8 Sightseer fails to get his (‘sightseer’ fails to get ‘his’ = gtseer = EGRETS) birds (EGRETS),
11 Thuggish leader (‘thuggish’ leader = T-) in Clare (-ENNIS) linked to shady business (RACKET) (TENNIS RACKET) is subject of underhand tactics in court (TENNIS RACKET),
15 There’s no difference (IDENTICAL) whatever way you look at it, it’s just more of the same (IDENTICAL),
16 Breaking up (= anagram indicator) soils, etc., (soils etc = SOLSTICE) comes at a turning point in the summer (SOLSTICE),
17 Old (O-) party (Fianna Fáil = -FF-) mastermind (-STAGE) (OFFSTAGE) in the wings (OFFSTAGE),
19 High-flyers overseas (Royal Air Force = RAF-) find international racing drivers (Fédération Internationale de l’Automobile = FIA = -FIA) (RAFFIA) can be useful for a bit of weaving (RAFFIA),
20 Count (CENSUS) wants to know can you speak Irish, for instance (CENSUS),
23 Fruit (OLIVE) starter of oranges (starter of ‘oranges’ = O-) is rotten to core (evil) – send it back (= reversal indicator) (evil = -LIVE) (OLIVE).